Blackberries (Rubus sp.) are a rich source of anthocyanins
and other polyphenolic antioxidants. Because of their antioxidant properties,
dietary polyphenolics have been associated with a reduced risk of various
degenerative conditions including certain cancers and disease. A number of
studies have been done to identify germplasm high in ORAC (oxygen radical
absorbing capacity) in Rubus species. The present study was done to determine
how the ORAC of blackberries was affected by fruit storage. Blackberries of
five cultivars, originating from the University
of Arkansas breeding program (all
tetraploids), grown in Lane,
Okla. and harvested in 1998 at
the shiny black and dull black stages of ripeness, were held at 2 oC, 95%
relative humidity for 7 days plus 2 days at 20 oC. Non-decayed berries were
freeze-dried and powder of drupelet and receptacle tissue (no seeds) was
extracted with acidified methanol. Samples were prepared for ORAC analysis
using a COBAS-FARA II spectrofluorometric centrifugal analyzer. No significant
differences were found between shiny and dull black fruit. ORAC values were
highest in 'Kiowa' and lowest in 'Shawnee'
fruit (4048 and 2690 mmol trolox/g freeze dried tissue, respectively). Values
averaged for stored fruit were slightly lower than for fresh berries (3110 vs
3393 mmol trolox/g, respectively). These results indicate that the ORAC of
these blackberry cultivars is not significantly increased at the latter stages
of ripeness or by fruit storage at 2 oC.